JPS63132947A - Method for treating molded polyamide article - Google Patents

Abstract

PURPOSE:To improve lubricity of a molded polyamide article and prevent deterioration of impact resistance, abrasion resistance, etc., caused by fluctuation of water absorption, by molding a polyamide, permeating an aqueous emulsion type lubricant, sufficiently fixing the lubricant and drying the molded article. CONSTITUTION:An aqueous emulsion type lubricating oil obtained by adding an emulsifying agent to a lubricant, e.g. petroleum based or polymerized olefinic coil, silicone oil consisting essentially of a high-molecular weight hydrocarbon component, etc., which is liquid or semisolid (grease form) at ordinary temperature and dispersing the resultant blend in water is permeated into a molded polyamide article at 70-120 deg.C temperature by a coating, dipping method, etc., and the excess sticking emulsion is preferably removed to sufficiently fix the lubricating oil at ordinary temperature or while heating and then dried by utilizing dry air, hot air, etc. Thereby treatment in which the lubricity of the above-mentioned molded article can be improved to prevent deterioration of impact resistance, etc., caused by fluctuation of water absorption is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to a method for treating polyamide molded articles.

[Conventional technology]

Polyamide is usually an acid amide bond (-C0N) I-
→ It is a general term for polymers having a fiber-forming ability, and among them, linear fiber-forming polymers are called nylon, such as nylon 6, nylon 46, nylon 66, nylon 610, nylon 7, nylon 8, nylon 9, nylon 10. ．． Nylon 11. It is already well known that a large number of materials such as nylon 12 or their copolymers or mixtures are produced on an industrial scale. and,
Compared to other plastic and metal materials, such polyamides have excellent mechanical strength, especially abrasion resistance, self-lubricating properties, light weight, moldability, heat and cold resistance, silence, chemical resistance, non-toxicity, and dye resistance. It is excellent in many respects, such as its properties, and in the field of plastic materials, it is widely used in various equipment parts such as bearings, bushes, gears, automobiles and other vehicle parts. It is also well known that in the field of textile materials, it is considered important as a synthetic fiber that can replace silk. However, in this polyamide, molecular force (hydrogen bond) acts between the oxygen of the carbonyl group (=C-0) in the main chain and the hydrogen of the adjacent amino group (=N11), and these groups become hydrophilic. Due to its nature, it may absorb moisture if left in humid air.
Or, if left in dry air, the absorbed moisture will be released, and the absorption rate will fluctuate in the range of θ to 14%.The degree of absorption varies depending on the type of polymer, but the amount of absorption at that time will affect the molded product. The mechanical properties of molded products are greatly affected, so even if a molded product has excellent mechanical properties such as abrasion resistance, lubricity, and impact resistance after absorbing a relatively large amount of water, As the amount of water absorbed decreases, the performance deteriorates, making it unusable and often causing various troubles. Therefore, this kind of water absorption of polyamide is a fatal flaw, and conventionally, water lubrication, solid lubricant (
For example, methods such as adding molybdenum disulfide, graphite, metal soap, etc.) and oil lubrication have been adopted, but methods such as essentially adjusting and stabilizing water absorption and improving wear resistance, lubricity, and impact resistance have been adopted. There were almost no attempts to do so.

Therefore, the inventor of the present invention proposed a polyamide machine part characterized by having a water and lubricant permeation layer on its surface, water absorption treatment and dehydration treatment after molding, and further developed a water-based emulsion in accordance with Japanese Patent Application No. 58-69818. A method for manufacturing polyamide mechanical parts is disclosed, which is characterized by heating and infiltrating mold lubricating oil. When a water and lubricating oil permeation layer is provided on the surface of a polyamide molded product in this way, it significantly improves the inherent lubricity of polyamide, and at the same time improves impact resistance and abrasion resistance due to fluctuations in water absorption, which are disadvantages of polyamide. It also showed a remarkable effect in preventing deterioration of mechanical performance such as, etc., and the dimensional stability after post-processing was also significantly improved. However, the method disclosed for producing such polyamide molded products usually involves immersing or enclosing the polyamide molded product in an atmosphere of hot water of about 70°C or higher or steam of about 120°C or lower for several hours to several tens of hours. After forcibly absorbing water, the water is heated to, for example, about 70 to 120°C, and then the pressure is reduced to, for example, several tens of 1 to 11 g or less to remove the absorbed water. Although the emulsion-type lubricating oil is heated and permeated, the disadvantage is that the pre-treatments, such as water absorption treatment and dehydration treatment after molding, are extremely complicated.

[Problem that the invention seeks to solve]

As described above, although a polyamide molded article with significantly improved properties can be obtained in the conventional techniques, there is a problem in that the processing method for obtaining it is complicated.

[Means for solving problems]

In order to solve the above problems, this invention adopts a method of treating polyamide molded products by infiltrating a water-based emulsion type lubricating oil after molding, fixing the lubricating oil sufficiently at room temperature or under heating, and then drying it. This is what I did.

The details will be described below.

First, the water-based emulgitane lubricant in this invention is a lubricant that is liquid or semi-solid (grease-like) at room temperature.
For example, petroleum-based oils mainly containing high molecular weight hydrocarbon components, synthetic oils such as olefin polymerized oils, diester oils, polyalkylene glycol oils, halogenated hydrocarbon oils, silicone oils, animal and vegetable oils, etc. alone or in combination. Mixed oils of more than one species, or modified oils by introducing groups reactive to acid amide groups, such as hydroxyl groups, carboxyl groups, epoxy groups, etc., and addition of modifiers required as lubricants. lubricating oil is dispersed in water by adding an emulsifier.If the emulsifier is hydrophilic and water-soluble, such as soap or alcohol, the lubricating oil will be dissolved in water in a transparent state. It is also possible.

Here, depending on the type of lubricant, a third substance having a catalytic effect may be added to cause a polymerization reaction within the permeation layer to change the lubricant to a lubricant with a larger molecular weight. Furthermore, if the lubricating oil emulsion is appropriately colored, it is possible to color the surface of the molded product and obtain a color effect, and at the same time, it is convenient for knowing the thickness of the permeation layer on the surface of the molded product.

Next, the type of polyamide used in the present invention is not particularly limited, and may contain carbon black, other pigments, fillers, reinforcing materials, etc., and has been widely used in the fields of engineering plastics and fiber materials. Any of the following may be used. Polyamides are usually processed by injection molding, extrusion molding, spinning, etc., which are carried out at temperatures of approximately 200 to 320°C, as well as blow molding, film (sheet) molding, sinter molding, centrifugal casting, powder coating, monomer casting, etc. Various molded products can be obtained by machining etc.

In addition, polyamide molded products have a short elapsed time after molding, and the drier the contact atmosphere, the less water absorption of the molded product, which is preferable.In infiltrating water-based emulsion type lubricating oil into such molded products, Although there are no particular limitations on temperature or time, in general, the lower the temperature, the longer the processing time (necessary), and even though a higher temperature is desirable to shorten the processing time, the higher the temperature, the more equipment Since this will increase costs and costs, resulting in an economic disadvantage, normally a water-based emulsion type lubricant is applied to the molded product at a temperature of about 70 to 120°C, or a water-based emulsion type lubricant is applied to the molded product at a temperature of about 70 to 120°C. The surface of the molded product can be kept fully covered with the lubricating oil emulsion for several tens of hours or less. On the other hand, after removing the excess lubricating oil emulsion that has adhered, preferably, the infiltrated lubricating oil is fixed at room temperature or under heating.

The behavior of the lubricating oil during this fixing process is not entirely clear, but the molded product is formed by the bonding of the lubricating oil itself or the bonding of reactive groups naturally or artificially introduced into the lubricating oil molecule with the polyamide. It is presumed that a new strong structure is formed in the area where the lubricating oil has penetrated. Generally, the higher the temperature (lower than the softening point of the molded product), the faster the various reactions during the fixing process, which is advantageous. In cases where the lubricating oil is susceptible to thermal deterioration, it is desirable to carry out the process at room temperature.

Furthermore, after such a fixing process, a drying process is performed, which is a process to make the fixing of the lubricant more complete and at the same time remove excess moisture, and as an extension of the fixing process. Alternatively, it may be carried out separately in separate strips, and the specific method may be a normal method using dry air, warm air, hot air, etc., and the end point may be the point at which the weight of the molded product stops changing. .

In addition, for bearings, bushings, gears, and other molded products that require high clearness, machining may be performed again for finishing at the end.

〔Example〕

Examples and comparative examples are shown below.

Example: Polyamide [manufactured by Toshi Co., Ltd.: Nylon CM10171] was injected into a mold at a cylinder temperature of 270 to 280°C, cooled to 80°C in the mold, taken out, and made into an outer diameter of 1911°C.
On both sides of the car, which has an inner diameter of 7 inches and a width of 9 holes, there are three fan-shaped depressions about 2 cranes deep and arranged concentrically at three locations at intervals of about 2.5 m.For sliding purposes. got wheels. This wheel is uniformly dispersed in an 80°C silicone oil solution (containing approximately 40% silicone oil (manufactured by Toshisha Co., Ltd.: Silicone TK20)) using a hydrophilic surfactant to make it easier to detect the thickness of the permeation layer. A small amount of coloring agent was added to make a brownish liquid), and the wheel was soaked for about 48 hours while being maintained at the same temperature to fully absorb water and silicone oil into the wheel surface layer. This was then heated to about 120° C. to fix the penetrating lubricating oil, and then dry it. The time required was about 1.
It was 0 hours. In order to evaluate the mechanical properties of the obtained wheel, a wheel of the same shape after injection molding without silicone oil solution treatment was used as a control product.
As a result of trying the r @ heavy rotation test of tr, it was found that the wheel obtained in the example according to the present invention still withstood the load even after 8 months had passed, whereas the control product could only withstand the load in the 800 kg load rotation test. It wore out and broke within 2 to 3 hours and became unusable. The wheels according to the present invention are not affected by the humidity in the atmosphere.
One or more of the characteristics that were comparable to the method disclosed in No. 9818 in which water absorption treatment and dehydration treatment are performed as pre-treatments were obtained when treated with a lubricating oil other than silicone oil, such as cottonseed oil. The same was true.

Comparative example: A wheel obtained by injection molding under the same conditions as the above example was heated to 80°C.
The sample was soaked in silicone oil (the same product as in the example, but did not contain water) heated to about 48 hours. 3000 of the wheels obtained
The results of the hg load rotation test were not much different from the wheels of the example.
It is thought that the adhesion of silicone oil affected the lubrication effect, but in a falling weight impact test in which a 5 kg falling weight piece was dropped from a height of 2 m, it was found that the fixed and dried wheels obtained in the example Although no abnormality was observed, the wheel obtained in this comparative example was destroyed, and it became clear that the impact resistance was significantly inferior.

〔effect〕

The polyamide molded product of this invention subjected to the above treatment is
Immersion of water and lubricating oil formed within the structure of the molded product i3N
This mechanism of action significantly improves the inherent lubricity of polyamide, and at the same time prevents the deterioration of mechanical properties such as impact resistance, abrasion resistance, and tensile strength due to fluctuations in water absorption, which are disadvantages of polyamide. Also, the dimensional stability after post-processing is extremely good. Since such good results can be obtained through simple processing, it can be said that the significance of this invention is extremely large.

Claims (1)

[Claims] A method for treating a polyamide molded article, which comprises infiltrating a water-based emulsion type lubricating oil after molding, sufficiently fixing the lubricating oil at room temperature or under heating, and further drying.